This invention relates generally to angle sensors and more particularly to angle sensors used to sense the wheel angular position of a vehicle steering wheel.
In automotive vehicles, subassemblies are installed which feature more and more electric circuitry serving the safety and/or the comfort or relief of the driver. ABS, slip control and yawing moment control are examples in this respect. Thus, electronic subassemblies constitute an ever increasing part in the manufacture and price formation of the vehicles. Therefore, endeavors are made to integrate more and more subassemblies with each other in order to reduce assembly steps and costs.
In addition to the prior art steering column switches, in the area of the steering wheel/steering column of a vehicle, there have been added devices for heating the steering wheel, the airbag, the hazard warning signal flasher, the steering angle sensor and the transmission device for supplying electric power to the subassemblies, flanged to the rotating steering wheel, from the electric power supply unit assembled fast with the chassis. The appropriate subassemblies are supplied by different manufacturers in separate housings which, then, are stacked on top of one another and are connected with one another both mechanically and electrically. Consequently, a series of mechanical and electrical interfaces results which not only are expensive to manufacture but which also require a comparatively large space and considerable effort and cost for the coordinating and tolerance rating of the individual subassemblies.
It is thus an object of this invention to suggest measures for simplifying the manufacture and assembly efforts of the subassemblies installed in the area of the steering column/steering wheel.
This invention consists in the constructional combination of the transmission unit and of the steering angle sensor in that one housing part of the electric power transmission unit simultaneously forms a housing part of the steering angle sensor. In an integrating process, it is, in principle, possible to proceed in such a manner as to captively support both the rotatable code disk and the rotatable lid of the electric power transmission unit each in one housing half and to then close the two housing halves, with the rotating parts facing each other, so that they are accommodated in a joint housing shut off against the outside. In doing so, however, attention has to be paid to the fact that the drive of the components to be rotatably driven, the code disk and the connection device for the airbag contacts, has to be effected via the cylindrical center aperture of the subassemblies in the area of the steering column. In order to have sufficient space for the mechanical and electrical interfaces of the electric power transmission unit, the individual units such as electric power transmission unit and steering angle sensor are placed on top of each other so that the lid of the one unit simultaneously at least forms one part of the bottom of the unit lying on top thereof. The inventive system, moreover, grants full freedom as regards whether or not all the units belonging to the system are actually installed. For instance, it is possible to install the electric power transmission unit even without the steering angle sensor by only mounting an appropriate bottom part instead of the steering angle sensor. As it must be taken into account that more and more subassemblies will be integrated into the steering wheel in order to achieve a simplified operability of the instruments and improve the safety of the vehicle, it is preferred to have the electric power transmission unit directly connected to the steering wheel while it will be possible to selectively couple the following building units to the transmission unit, with a steering column switch being coupled to the electric power transmission unit in addition to the steering angle sensor or instead of the same.
In a preferred embodiment, building units are arranged centrally relative to the steering column. The individual subassemblies essentially feature the shape of hollow annular bodies that may be inserted into, or rather interlocked within, each other or just be stacked on top of each other. As far as the housing lid must be rotatable relative to the housing bottom lying beneath it such as is the case with regard to the lid of the electric power transmission unit the locking system should be chosen so as to keep the lid rotatable relative to the bottom. This may be done, e.g., by providing a surrounding groove in the lid engaged by an appropriate projection of the bottom.
A steering angle sensor can be one of the building units. This enables the code disk to be directly driven by the steering wheel in a relatively simple way. With the housing lid being formed by the lid of the electric power transmission unit, a dual function will be achieved as the lid serves as mechanical and electrical interface, on the one hand, and simultaneously drives the code disk of the second-building-unit steering angle sensor placed underneath thereof, on the other hand.
In a further embodiment, a steering column switch is selected as a building unit into the subassembly in addition to the steering angle sensor. The steering column switch, too, is provided with elements actuatable by the rotation of the steering wheel such as the reset cam of the direction indicator reset device. The mode of operation of such a resetting action is described for instance in the applicant""s patent application P 44 18 328.3. Thus, e.g., the lid of the electric power transmission unit cannot only drive the code disk of the steering angle sensor but also the reset cam of the steering column switch. It is thus recommendable to coordinate the design of the housing parts so that either the tongue of the electric power transmission unit will drive both the code disk of the steering angle sensor and the reset cam of the steering column switch or so that the steering angle sensor is dispensed with and the electric power transmission unit, without any constructional change to it, will only drive the reset cam of the steering column switch in case there is no need for a steering angle sensor in the vehicle. As a result, this means that the housing lid of the steering column switch should feature the same configuration as the lid of the steering angle sensor so that the steering angle sensor and the steering column switch are interchangeable relative to the electric power transmission unit.
Preferably, the steering column switch is located beneath the steering angle sensor and the electric power transmission unit. As in many cases, however, no use is made of a steering angle sensor it may likewise be expedient to design the steering column switch so as to enable additional assembly of the steering angle sensor beneath the steering column switch in case of demand.
Preferably, at least two building units are jointly activated by one drive segment coupled to the steering wheel. The use of one drive segment can be achieved by using an actuating tongue to drive both the code disk of the steering column switch and the reset cam of the steering column switch.